The present invention relates to apparatus for loading and unloading sheets of imaging material (e.g., photographic film) from the imaging portion of an image recorder such as a still camera or film recorder.
One type of photographic apparatus that uses photosensitive film is a film recorder. In a conventional film recorder, a light beam from a cathode ray tube ("CRT") or the like is controlled by a deflection system to scan across a stationary frame of photographic film to expose the film with an image. Typically, the images are generated by a computer for the production of slides, transparencies, photographs or the like. Alternatively, the images can comprise natural images acquired by a scanner or television camera for subsequent processing by a computer.
Known film recorders, such as those sold under the trademarks "SOLITAIRE" and "SAPPHIRE" by Management Graphics, Inc. of Minneapolis, Minn., U.S.A., typically include a light source such as a CRT for producing a beam, a deflection system for scanning the beam across the face of the CRT, a system control and central processor unit ("CPU") for controlling the deflection system, and a camera (i.e., "film transport"). The latter component may include a film transport body, lens, lens mounting assembly, aperture plate, film plate, and film transport mechanism. The film may be provided in rolls or strips, or in individual sheets.
The present invention relates to the automatic feeding of individual sheets of film to the exposure area ("imaging station") of a film recorder or other imaging equipment. The term "large format" refers to cameras that use sheet film, typically four inches in width and five inches in height or larger. Large format cameras offer better quality, less graininess and a much greater range of tonal values than smaller film, such as 35 millimeter film. However, the use of sheet film requires the loading of single sheets, one at a time, into the camera for each exposure and subsequent removal of each sheet before the next sheet of film can be loaded. During this inconvenient process, the sheets of film must be protected from light.
An automatic sheet feeding film holder has been proposed in U.S. Pat. No. 4,779,112. The patented apparatus can be attached to or inserted into a processing area, such as a camera or enlarger, and is capable of holding a stack of sheets of photographic film, both before and after exposure. Sheets are fed one at a time from a supply stack into a processing area, and then retrieved while a new sheet is being loaded. The apparatus disclosed in the patent has various drawbacks. For example, a common input/output drive roller is used to load a new sheet into the processing area while an already exposed sheet is being retrieved from the processing area. As a result, if it is desired to expose fewer than all of the sheets in the supply stack, there is no convenient way to prevent an unexposed sheet from being loaded into the processing area when the last exposed sheet is retrieved therefrom. This may result in the wasting of a sheet of film, if the apparatus is removed from the camera to be taken into a darkroom, in which case the sheet of film currently in the exposure area of the apparatus will be exposed to light and destroyed.
The apparatus disclosed in the aforementioned patent also has a cumbersome structure for allowing a photographer to insert a fresh stack of film sheets in the apparatus and to retrieve a stack of exposed sheets.
It would be advantageous to provide an improved automatic single sheet feeder for photographic apparatus, that overcomes the disadvantages of the prior art. The present invention provides such apparatus.